Hang on to your dry flies too- the bigger ones like Hexes and other Drakes, Stimulators, Hoppers and large Wullffs are a good choice. A lot of rivers and streams in the East and midwest get a White Fly hatch around dusk and into early evening during August. It's a large white mayfly that often hatches in such huge numbers that flight s are often picked up on weather radar. It's around a size 12 or 14, so something easy to see in low light, and sturdy construction like a White Wulff is a good choice. You might ask around to see if you can find smallmouth streams known for this hatch in your area.
Other trout flies you probably have that should work are stuff that pushes a lot of water like muddlers, marabou muddlers, zonkers as well as most any streamer or bucktail and bugger you might have.
Other good choices for smallmouth:
Traditional bucktail Clousers and variations like the Foxee Clouser, crayfish imitations, hellgrammites to lose among the rocks,
Top water stuff like Gurglers or Sneaky Petes, deer hair bass bugs to blurp along the surface
and stuff that floats at rest but dives on retrieve like Dahlberg Divers are also good choices for Smallmouth.
I like to try and get them on top if i can, but often go to an unweighted Muddler, or Marabou Muddler (or a similar fly that pushes a lot of water like the Flash Dancer) on a short heavy leader off a sink tip fly line. The combination of floating fly and sinking tip gets the fly down but helps to keep it out of the rocks. Here's a pic and recipe for a Flash Dancer:
Good luck-- let us know how you do.